1. Field of the Invention
The present invention generally relates to an emulsified polymer containing an aqueous polyurethane component and having a high solids content, a method for production of emulsified polymers, and a water-based paint grade resin composition using emulsified polymers as an applied film-forming component.
2. Description of Related Art
In the field of coating materials, inks, adhesive agents, etc., the conversion of products using organic solvents to those using water as a vehicle (water-based products) is being promoted with a view to conserving natural resources, securing environmental hygiene, protecting the environment against pollution, ensuring detoxification of dangerous substances, and so on. Generally, air driable water-based paints use an acryl type copolymer emulsion as a component of the vehicle. The emulsion, though capable of allowing production of an applied film excelling in weatherability and rigidity, reveals deficiency, inter alia, in resistance to water and resistance to pollution. Meanwhile, the market is experiencing an increased need for improving the elasticity and toughness of applied films. The feasibility of using a urethane resin in air drying water-based paints is being studied.
A cold-setting type water paint comprising a carbonyl group-containing aqueous polyurethane resin and a hydrazide compound has been proposed, for example, in Japanese Examined Patent Publication No. 8-3,019 as a water-based paint including urethane. Though this paint can form an applied film excellent in resistance to water, etc., it has a low solids content, and the solids content of the aqueous polyurethane resin is only increased with difficulty. When it is used as a coating material, it has the problem of inferior workability in coating as evidenced by its tendency to sag. Further, the known technique of grafting a urethane and an acrylic monomer does not significantly heighten the solids content because the grafting imposes a limit on the monomer composition and the ratio of urethane to acrylic monomer.